Fuel injection system for internalcombustion engines



March 30, 1948. ND 2,438,663

FUEL INJECTION SYSTEM FOR INTERNAL-COMBUSTION ENGINES Filed Dec. 29, 1945 2 Sheets-Sheet 1 March 30, 1948.

FUEL INJECTION SYSTEM FOR INTERNAL-COMBUSTION ENGINES L. s. GREENLAND 2,438,663

Filed Dec. 29, 1945 2 Sheets-Sheet 2 Patented Mar. 30, 1948 FUEL INJECTION SYSTEM FOR INTERNAL- COMBUSTION ENGINES Leonard Sidney Greenland, Weaton-snper-Mare, England, assignor to H. M. Hobson Limited, London, England, a company of Great Britain Application December 29, 1945, Serial No. 638,130 In Great Britain February 12, 1945 This invention relates to fuel injection systems for internal combustion engines of the type in which fuel is delivered under pressure to the engine, or to the induction system, through a main fuel conduit containing a variable area meterin orifice, the effective area whereof is varied as a desired function of boost pressure, and preferably also of exhaust back pressure and induction temperature as well, and which includes means for maintaining across the metering orifice a pressure difierence (hereinafter referred to as the metering pressure) which varies as a desired function of engine speed.

In a system of this character the metering pressure will be related to engine speed according to a definite law determined by the nature of the device for regulating the metering pressure and it is preferred to utilise for this purpose an engine driven centrifugal impeller, some fraction of the pressure difference developed by which is applied across the metering orifice. The metering pressure will, in this case, vary as the square of the engine speed.

On the fuel/air ratio determined by the device for regulating the metering pressure to accord with changes in engine speed in conjunction with the devices for correcting the area of the metering orifice in accordance with variations in the other variables above referred to, it is necessary however to superimpose additional corrections to suit specific conditions of engine working. Such corrections are required:

(a) to provide slow running adjustment,

(b) to give an enrichment in mixture strength from weak cruising to normal cruising,

(c) to provide an enrichment in mixture strength during periods of acceleration.

According to the invention, three supplementary fuel conduits are provided, one being con- I trolled by a slow running valve, one by a weakto-normal enrichment valve andthe third by an accelerator pump, and a single manually operable linkage controlled by the Pilot's throttle lever is utilised to operate both valves and the accelerator pump to effect the aforesaid corrections automatically as an incident to adjustment of the position of said lever.

The conduit controlled by the accelerator pump will be arranged in parallel with the metering orifice, and the accelerator pump will operate to feed additional fuel to the engine through that conduit only when the pflots lever is given a sudden movement to increase the engine power. The weak-to-normal enrichment valve may likewise control a conduit in parallel with the me- 6 Claims. (01. 123-119) tering orifice and in this case it will be closed for positions of the pilots lever. between slow running and weak cruising, and opened when the pilots lever is moved into the normal cruising position or to a position selecting higher power from the engine than this. Alternatively,'however, this valve may, as described in U. S. patent application Serial No. 533,120, new Patent No. 2,419,171, control a conduit for bleeding fuel from the entry side of the metering orifice, in which case it will be open only for positions of the pilot's lever selecting a power less than that required for normal cruising, and closed when the pilot's lever is m 'ived to a position selecting higher power. The slow running valve may also control a conduit in parallel with the metering orifice, in which case it will be arranged to be opened only atslow running, and will enrich the mixture at slow running. In some cases, however, it may be desired to weaken the mixture at slow running. The slow running valve can then be disposed in a conduit for bleeding fuel from the exit side of the metering orifice and arranged to open only at slow running. As a further alternative, the slow running valve may, as described in U. S. patent application Serial No. 533,120, be employed to control a bleed pipe leading from the entry side of the metering orifice.

Preferably the linkage is arranged so as to actuate a fuel cut-off valve, when the pilots lever is moved beyond the slow running position in the direction to reduce engine power.

In Figs. 1-4 of the accompanying drawings are shown diagrammatically four examples of fuel injection systems according, to the invention intended for installation in aircraft engines. Like reference characters designate like parts throughout the figures.

Considering first the arrangement shown in Fig. 1, fuel is fed from an inlet ill by an engine driven gear wheel pump H along a main fuel conduit I! to a metering orifice 25 the efi'ective area of which is controlled by a needle 24. The

pump II is provided with a diaphragm-operated via pipe 36.

The pressure difference across the meterin orifice 25 is arranged to be substantially proportional to the square of the engine speed utilising 3 the difierence of pressure generated across a engine driven centrifugal impeller 31. The pressure at the tip of the impeller is applied via conduit 38 to the upstream side of the orifice and a desired proportion of the impeller eye pressure is applied to the downstream side of the orifice by means of a flexible diaphragm'39 operating a pressure regulating valve 40, as described for example in U. S. Patent No. 2,374,844. The left hand side of the diaphragm 39 is exposed to the impeller eye pressurevia a conduit 44, while the right hand side is exposed to the fuel pressure at the exit of the metering orifice.

After passing the metering orifice 25, the metered fuel enters a chamber I9 and passes thence through the pressure regulating valve 40, pipe 45, and balanced discharge valve 45 to a nozzle 41 through which it, is injected into the induction pipe I5.

The diaphragm 39 is coupled to the stem of the pressure regulating valve 40 by means of a bell crank lever 48 mounted on a fixed pivot 49. The diaphragm 39 is loaded by a spring 50 which serves to balance the forces exerted by the fuel on the pressure-regulating valve 40 and also to proin my copending U. S. application Serial No.

638,127, filed December 29, 1945.

The effective area of the metering orifice is varied as a desired function of boost pressure and exhaust pressure by a pair of balanced capsules I3, I4 disposed in the chamber I9. The capsule I3 is subjected to boost pressure internally, being connected to the induction pipe I5 by a conduit I6, and the other capsule [4 which is of exactly the same external shape and area, is divided into two compartments one of which I4 is partly evacuated and the other I4 subjected internally to exhaust back pressure, being connected to the exhaust pipe I8 by a conduit II. The outer ends of capsules I3 and I4 are anchored to the walls of the chamber I9 andtheir inner ends are joined by a member II3, carrying a trunnion II4, on which is pivoted a lever 20. The forked end I of lever 20 is pivoted at 22 to a Bourdon tube assembly 23, while lever 20 is pivoted at its other end I2I to the stem I22 of the needle 24. Variations in boost pressure and exhaust back pressure will effect appropriate adjustment of the needle 24 by rocking the pivoted lever 20 about its point of attachment 22 to the Bourdon tube assembly 23. This effects adjustment of the needle 24, under the control of a thermometer bulb 2| in the induction pipe I5, to correct the fuel flow for changes in induction temperature, the lever 20 effecting such adjustment by rocking about the trunnion II4.

With the apparatus as so far described, the fuel flow through the metering orifice 25 will be a substantially linear function of engine speed, and will be appropriately varied to suit changes in boost pressure, induction temperature and exhaust back pressure. The boost pressure is selected by a pilots throttle lever, not shown, which operates a variable datum boost control device, also not shown, as described in U. S. Patent No. 1,995,800. A lever 52 is coupled to the pilot's throttle lever and operates through a mechanical linkage to effect the further adjustments in fuel flow now to be described.

The pilot's throttle lever is movable from a slow running position (3.1%.) through a cruising range to a full throttle position (F. T.) In the cruising range a weak mixture is desirable for economy. When however the engine power exceeds a given limit, known as the weak-to-normal enrichment point, it is necessary to provide an enrichment in the mixturestrength. At slow running the weak cruising mixture is not suitable and an adjustment in mixture strength is required, this being either an enrichment or a weakening according to the type of engine. Thus a weaker mixture is required in-the case of engines exhibiting'a high degree of boost reversal at or near slow running, while with engines not exhibiting this phenomenon it is desirable to enrich the mixture at slow running. Extra fuel is also required during periods of acceleration. All these requirements are met by a. single mechanical linkage controlled by the lever 52, but before explaining how this is done, it will be convenient to explain that additional enrichment of the mixture, beyond the rich mixture corresponding to normal cruising, is required for take off and climb. This is provided by the profiling of the needle 24, the narrower portion I24 of which is operative under these conditions.

The weak-to-normal enrichment is provided by a valve 53 which controls a supplementary conduit 54 in parallel with the metering orifice, the flow through conduit 54 being regulatable by a screw 55 cooperating with a restriction 55. Valve 53 is held closed by its spring 51 when the pilots lever is in a position between slow running and weak cruising. When the lever is moved to select a power higher than that corresponding to this range, a link 58 connected to lever 52 rocks a lever 59 anticlockwise about a fixed pivot 60, causing a finger 6| on lever 59 to open the valve 53 and enrich the mixture by virtue of the extra fuel supplied through conduit 54.

The slow running adjustment is provided by a valve 62 controlling a supplementary conduit 63 which (when open) provides a flow in parallel with the metering orifice to chamber I9 through a restriction 64 which can be controlled as to area by a screw 65. At slow running the valve 62 is open, as shown, to enrich the mixture.

.When the lever 52 moves anticlockwise out of the slow running position, a finger 66 thereon moves away from valve 62, allowing a spring 58 to close the valve.

Extra fuel for acceleration is provided, via supplementary conduit 69 by an accelerator pump III which is operated, via link II and lever I2, which turns on a fixed pivot I3 when and only when the pilots lever is moved suddenly in the direction to increase the engine power. The lever I2 is connected to a hollow valve ilIl.v When lever 52 is moved in the direction to accelerate, the valve is drawn away from a seatingon a diaphragm I59 to allow extra fuel to pass to the engine through conduit 69. Follow-up movement of the diaphragm I59 by spring I60 to close valve 90 is delayed by a restriction 92, the efi'ec tive area of which is adjustable by a screw ,SI. A

spring ill to close the valve 46 and cut off the fuel supply.

Adjustment for-initial tuning purposes is provided by an orifice 4| adjustable by a screw 42, through which a small quantity of fuel may be allowed to by-pass the metering orifice. 82 is a normally closed priming valve through which fuel may be supplied to the engine from inlet II! by a priming pump prior to starting of the engine. At this time pump H is of course inoperative. i

In the arrangement shown in Fig. 2, the weakto-normal enrichment valve I53 controls a conduit I56 for bleeding fuel from the conduit I2 to the suction side of the pump II. The valve I53 is open, as shown, when the pilot's lever is in a position to select a power requiring weak mixture. wise to select a power in excess of that corresponding to weak-to-normal enrichment point finger GI moves away from valve I53, allowing spring 51 to close the valve and so enrich the mixture.

In the case of Figs. 3 and 4, the slow running adjustment is arranged to weaken the mixture at slow running instead of enriching it as in the case of Figs. 1 and 2. In Fig. 3, the slow running valve controls a conduit for bleeding fuel from the inlet of the metering orifice 25 to the suction ide of the pump II. As before, valve I62 is open at or near slow running only, and under other conditions closes to prevent subtraction of the fuel from the main metering supply. The arrangement of Fig. 4 is very similar, but in this case valve I82 controls a conduit 263 for bleeding fuel from the chamber I9 at the exit side of the metering orifice.

What I claim as my invention and desire to secure by Letters Patent is:

1. In a fuel supply system for an internal combustion engine, comprising a main fuel conduit, a variable area metering orifice in said conduit, a fuel pump for feeding fuel under pressure along said conduit and through said metering orifice, means for varying the effective area of said oriflce as a desired function'of boost pressure, and means for maintaining across said orifice a metering pressure which varies as a desired function of engine speed and thereby controlling the ratio of fuel to air in the mixture supplied to the engine, the combination with a pilot's throttle lever, movable from a slow running position through a weak cruising range to a normal cruising position and beyond to select higher power from the engine, of a first supplementary fuel conduit, a slow running valve for controlling the flow of fuel through said first supplementary conduit, a second supplementary fuel conduit, a weak-to-normal enrichment valve for controlling the flow of fuel throu h said second supplementary conduit, a third supplementary conduit in parallel with the metering orifice, an accelerator pump for feeding fuel through said third supplementary conduit, all of said supplementary When however lever 52 moves anticlockconduits, when in operation, providing passages alternative to the metering orifice for the fuel supplied by the fuel pump, and a single manually operable linkage controlled by the pilot's throttle lever and arranged to operate both valves and the accelerator pump automatically and as an incident to movement of said lever, and by the resultant control in the flow of fuel through said supplementary conduits to provide an adjustment in the fuel flow at slow running, to give an enrichment in mixture strength on movement of said lever from weak cruising position to normal cruising position, and to provide an enrichment in mixture strength during periods of acceleration.

2. Apparatus as claimed in claim 1, in which the second supplementary fuel conduit is in parallel with the metering orifice, and the weak-tonormal enrichment valve is arranged to open to permit fuel to flow through said conduit, only when the pilot's throttle lever occupies a position defined, as to the lower limit of engine power, by the normal cruising position.

3. Apparatus as claimed in claim 1, in which the second supplementary fuel conduit serves to bleed fuel from the entry side of the metering orifice, and the weak -to normal enrichment valve is arranged to open to permit fuel to flow through said conduit only when the pilot's lever' occupies a position selecting an engine power less than that required for normal cruising.

4. Apparatus as claimed in claim 1, in which the first supplementary fuel conduit is in parallel with the metering orifice, and the slow running valve is open to permit of fuel through said conduit at slow running only, thereby enriching the mixture at slow running. a

5. Apparatus as claimed in claim 1, in which the first supplementary fuel conduit is arranged to bleed fuel from the entry side of the metering orifice, and the slow running valve is open to permit of fuel through said conduit at slow running only, thereby weakening the mixture at slow running.

6. Apparatus as claimed in claim 1, comprising a normally open cut-off valve, and a member forming part of said linkage for closing said cut-off valve to interrupt the main supply of fuel to the'engine when the pilot's lever is moved beyond the slow running position in the direction to reduce engine power.

- LEONARD SIDNEY G nnrnaancns crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,874,844 Stokes May 1, 1945 2,397,984 Schorn Apr. 9, 1946 FOREIGN PATENTS Number Country Date 429,682 Great Britain June. 4, 1935 523,895 Great Britain July 25, 1940 

